@(do
   (defmacro with-output-to-string ((var) . forms)
     '(let ((,var (make-string-output-stream)))
        (progn ,*forms (get-string-from-stream ,var))))

   (let ((x (with-output-to-string (*stdout*)
              (format t "world!"))))
     (format *stdout* "Hello, ")
     (put-line x)))